1. Field of the Invention
This invention relates to a camera having an auto focus device which drives a phototaking lens in accordance with the output of a photoelectric element array on which the image of an object to be photographed is formed, and more particularly to a single lens reflex camera in which the light beam from the phototaking lens is directed via a movable reflecting mirror to a finder and said photoelectric element array.
2. Description of the Prior Art
In a single lens reflex camera, a photoelectric element array for the detection of the in-focus of the phototaking lens, due to its necessity of being disposed at the imaging position of the lens, is provided within or near the finder optical system of the camera or in the interior of the camera body, and in any case, it is disosed rearwardly of a movable reflecting mirror. Thus, the object image formed on the photoelectric element array via the mirror during in-focus varies with the movement of the mirror resulting from a photographing operation. A technique whereby the operation of a focusing device is disabled in response to the movement of the mirror in order to prevent the focusing device from driving the phototaking lens in response to the variation of the image is known from Japanese Laid-open Utility Model Application No. 85233/1975. In this technique, however, at least minute displacement of the mirror itself or a mirror driving mechanism occurs before the operation of the focusing device is restrained, and this leads to an undesirable possibility that the phototaking lens is driven particularly where use is made of a well responsive photoelectric element and focusing device. Accordingly, as regards such minute displacement, namely, a minute fluctuation of the image on the photoelectric element array caused after the in-focus of the phototaking lens with respect to the object to be photographed has been completed, it is desired to reduce the aforementioned responsiveness.